In mobile devices, noise reduction technologies greatly improve the audio quality to regain speech intelligibility, especially for the far-end listener. The near-end listener, located in noisy environment, also experiences reduced speech intelligibility of the far-end talker.
A conventional Dynamic Range Controller (DRC) is typically used in modern mobile phones audio chains for voice calls. A use of DRC in audio processing systems is described in U.S. Pat. No. 8,626,516 (Zeng et. al.), which is incorporated herein by reference. The DRC is often applied on the received signal in order to maximize the loudness of the incoming speech for the mobile device user. However, when the DRC is tuned aggressively in an attempt to make the sound louder, some speech sounds, like the fricatives, are too much emphasized and sound very harsh, resulting in a poor subjective quality.
To improve the speech intelligibility in noisy environments, the Active Noise Cancellation (ANC) is an attractive proposition for headsets and the ANC does improve audio reproduction in noisy environment to certain extents. The ANC method has less or no benefits, however, when the mobile phone is being used without ANC headsets. Moreover the ANC method is limited in the frequencies that can be cancelled.